After he began his Major League career with back-to-back wins, Lyons struggled in his last four outings, surrendering four or more earned runs in each. It culminated in an early exit Friday, when he allowed four earned runs on three hits and three walks in just 1 2/3 innings. Lyons posted a 5.51 ERA through six starts.

Manager Mike Matheny said the lefty will be used as a starter in Memphis and that he would like Lyons to focus on his control of his fastball in the strike zone. "We gave him a list of a couple things to work on, but for the most part, it has everything to do with the fastball location," Matheny said.

Blazek, who will wear No. 67 with the Cardinals, was added to the Major League roster for four days in May, but he did not pitch in any games. The Cards' No. 8 prospect, according to MLB.com, Blazek is one of 10 rookie pitchers to appear on the active roster this season.

"I'm glad to be back," Blazek said. "I'm definitely ready. I had a couple of days off, so I feel good. I'll hopefully get in there."

The Cardinals selected Blazek with the No. 1,068th selection in the 2007 First-Year Player Draft. He posted a 2.31 ERA in 11 2/3 innings at Memphis, and he allowed just two earned runs on 11 hits in 19 2/3 innings with Double-A Springfield earlier this year.

Although he didn't make an appearance with the club in his last big league stint, Blazek was called up from Double-A and made the move to Triple-A when he was sent back down to the the Minors on May 29.

"He's getting promoted when he gets demoted," Matheny said. "When he came up, there just wasn't an opportunity. Every game was tight. Tried to get him in a couple times, got him hot twice, just didn't work out. But we're going to need him. He's going to have to come up and throw some innings."

With Joe Kelly unavailable after tossing 77 pitches in an extended relief appearance Friday, Blazek will provide a fresh arm out of the bullpen. The 6-foot, 200-pound right-hander last pitched Thursday, when he went two innings against the Rangers' Triple-A affiliate, allowing one earned run on one hit and two walks while striking out two.

Four of Blazek's eight appearances have been two innings. As Kelly rests, the Cardinals may need to call on Blazek to soak up innings in relief.

"He's been the best down there," Matheny said. "His efficiency and just getting outs. He's been able to throw a couple innings and has done it well. [He] has proved to our development folks that he's ready for it."

Blazek made his Major League debut in the ninth inning of Saturday's 4-2 loss to the Rangers, striking out Leonys Martin and Jurickson Profar and retiring Ian Kinsler on a groundout to first.

Chad Thornburg is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.